The first background art is as follows.
An analog watch that has a load-compensation function, this watch having a stepping motor that is driven by drive pulses, a drive judging means that observes movement of a rotor after a normal drive pulse is applied to the stepping motor and judges whether or not drive was correctly done, and a compensation drive pulse supplying means which, if the judgment was made by the drive judging means that drive was not completely done, supplies a compensation drive pulse to a drive circuit, is already known in the form of a product.
The principle of the load-compensation function is that of performing hand drive at each step with a drive pulse that has an amount of energy that is close to the minimum required energy, and observing the waveform of the electromotive voltage generated in the drive coil by means of the movement of the thus-driven rotor.
If a characteristic waveform is detected, such as occurs when the rotor is not capable of rotating normally through one step, this occurring during drive of the calendar mechanism, and when attached dirt or the like place a suddenly increased load, a compensation pulse having a larger energy (for example, with a larger time width) is immediately supplied once again so that the rotor is reliably driven by one step.
By doing this, the average power consumption from the drive pulses is reduced, so as to lengthen the life of the battery, and misoperation (delay) of the watch is eliminated.
The above-noted technology is already widely applied in electronic watches.
One known publication that discloses this technology is, for example, the Japanese Examined Patent Publication (KOKOKU) No. 8-33457.
In the embodiment shown in FIG. 1 of the above-noted publication (FIG. 6 in this application), a first drive inverter 18, a second drive inverter 19, and the associated circuitry form a stepping motor drive circuit, while a coil open/close pulse supplying means 20, a detection circuit 31, a first rotation detection signal storage circuit 32, a second rotation detection signal storage circuit 33, and the associated circuitry form a drive judging means. A compensation pulse supplying means 50 is also provided.
The stepping motor in the above-noted background art is configured as shown in FIG. 2 (FIG. 7 of this application).
Let us examine the load compensation technology as presented in the above-noted publication. As shown in FIG. 5 of the above-noted publication (FIG. 8 of this application), a voltage pulse having an overall width of 5 ms and which is finally broken up is supplied alternately every 1 second to the ends of the drive coil 28 of a two pole stepping motor as the normal drive pulse.
Each time the rotor 29, which is formed by a permanent magnet, is driven, it does not stop immediately when the drive pulse stops, but rather exhibits free vibration several times, this vibration inducing a voltage in the coil 28.
The waveform thereof naturally reflects the movement condition of the rotor 29, and in the case in which the rotor has completed a feed operation of one step normally, a coil current waveform such as shown in FIG. 4 (FIG. 9 of this application) is obtained.
However, if the gear train load is large, so that the rotor could not rotate normally, a coil current waveform such as shown in FIG. 7 (FIG. 10 of this application) is obtained.
In the case in which the normal drive pulse just barely results in normal rotation, a coil current waveform such as shown in FIG. 10 (FIG. 11 of this application) is obtained.
To observe the voltages waves induced by rotor movement that cause these currents, it is necessary during the free vibration of the rotor, to ground one end of the coil and to continuously or intermittently observe the voltage appearing on the other end, which is left open.
Because of the above, using a coil open/close signal (a narrow pulse that controls the inverter of the drive circuit, this being generated continuously, for example, 1 ms after the completion of the normal drive a predetermined number of times, for example, 13 times, at a 1-ms interval (as shown in FIG. 3 (d), FIG. 12 (d) of this application)), one of the end of the coil 28 is opened intermittently, the induced voltage appearing when that occurs (which is amplified as a result of a sudden change in the impedance) being detected by the detection circuit 31.
In the case of normal rotation, as shown in FIG. 4 (FIG. 9 of this application), because the induced voltage exceeds a threshold value (Vth) of the detection circuit on same times, the first rotation detection signal storage circuit 32 maintains its condition, after which a switch is made to the detection of the induced electromotive voltage at the other end of the coil.
Additionally, when the induced electromotive voltage exceeds the threshold value of the detection circuit on some time, the second rotation detection signal storage circuit 33 (which operates by counter 34 for only a short time) holds that condition.
If both the first and the second rotation detection signal storage circuits store an induced electromotive voltage that exceeds the threshold value, because the compensation drive pulse (FIG. 3 (c); FIG. 12 (c) in this application) that is generated when the subsequent free vibration of the rotor comes to rest need no longer be supplied to the drive circuit, gates are closed to block this. The circuitry transitions to a condition in preparation for drive judgment of the next normal drive.
In the case in which a feed error occurs as shown in FIG. 7 (FIG. 10 of this application) in the background art, after normal drive although the detection of an induced electromotive voltage that exceeds the threshold value is stored in the first rotation detection signal storage circuit 32, the second rotation detection signal storage circuit 33 maintains its condition even up until the last coil open/close signal and never stores the same condition in which an induced electromotive voltage exceeds the threshold value, as mentioned above.
In this case, a compensation drive pulse is applied to the same drive inverter as for normal drive. The overall width of the compensation drive pulse exceeds twice the width of the normal drive pulse, so that the stepping motor is supplied a sufficient amount of energy as drive is performed again, thereby making up for the delay caused by the missed drive.
In case in which, in the background art, normal rotation just barely occurs as shown in FIG. 10 (FIG. 11 in this application), after normal drive, at quite late a point in time the first rotation detection signal storage circuit 32 stores the detection of an induced electromotive voltage that exceeds the threshold value. The switched second rotation detection signal storage circuit 33 ultimately becomes the same at end of the operating period.
Because both detection signal storage circuits have operated, the supply of a compensation drive pulse is blocked.
The reason that the two detection signal storage circuits are switched sequentially in the background art is to improve the accuracy of judging drive, in consideration of the fact that the swing of the free vibration of the rotor is in both directions, so that the induced electromotive voltage appears sequentially as positive and negative.
The second background art will now be described. The principle thereof was known at the time of the inception of quartz-type electronic watches, but has come to be used in products starting several years ago. This is the so-called self-winding electric generating technology.
FIG. 3 in this application is a plan view of an example of a wristwatch that is an embodiment of the present invention.
Since FIG. 2 can also be used for explaining a plan-view arrangement of the background art in which two stepping motors are arranged, the background art will be described using the example of FIG. 3.
When an eccentric weight 14, which is pivotally supported within the wristwatch is rotated by either gravity or the movement of the art, this rotation is amplified by the gear train 15, and a rotor 12 of an ultra-compact electrical generator 10 is rotated at high speed, this causing generation of electricity in a coil 11.
The structure of the coil 11, the rotor 12, and a stator 13 of the electrical generator 10 are almost entirely the same as or similar to the structure of a stepping motor formed from a two-pole permanent magnet.
The materials, dimensions and coil specifications of the above-noted stepping motor for the electrical generator are selected appropriately so as to achieve the required electrical generating capacity, and so that housing within the wristwatch module is possible.
In terms of the details of a specific example of the placement condition between the stepping motor and the generator mechanism in the above-noted example, although a detailed drawing is not shown, in the case of a configuration with an electrical generator 1 and one stepping motor 6, as shown in FIG. 1, it is desirable that the two coils, which are parts having a large thickness within the round module, be arranged on both sides of the center of the watch, so that they form an approximate V shape. (Upon first view, this resembles a double-motor multifunction watch arrangement of the past. There is a round secondary cell located at the opening of the V shape.)
Additionally, as shown in FIG. 3, within the round module, are disposed two stepping motors 61 and 62, these being disposed at the sides of the watch's center axis, which joins the electrical generator 10 and the secondary cell 31.
In both of the examples cited, the rotor diameter and coil length of the electrical generator 10 are less than twice that of stepping motors 61 and 62, but compared alone, the amount of surface area occupied by the electrical generator 10 is greater.
The electricity generated by the rotation of the rotor 12 caused by arm movement is alternating current, and the voltage thereof is irregular with respect to time. This non-time-constant generated AC current is rectified and charges a secondary cell 31 or large-capacitance capacitor, this being consumed in steady-state fashion a little amount at a time as energy to operate the watch mechanism.
In the above-noted self-winding watch mechanism as well, it is desirable that the steady-state power consumption to operate the watch mechanism be small, as this enables the eccentric weight 14 and electrical generator 10, and thereby the overall watch, to be made small, and enables some extension of the operating life in the condition in which the watch has been removed from the wrist (this normally being several days).
With respect to these requirements, an extremely desirable power-saving technology that is highly effective is use in combination with the load-compensation function that is described above as the first background art.
Merely combining the first and second background arts, however, results in a problem, which is the magnetic noise generated by the generation of electricity causes misoperation of the drive judging means of the load compensation function.
Specifically, when the rotor 12 of the electrical generator 1 (10) rotates at high speed intermittently with irregularity, an alternating magnetic flux is generated in the magnetic circuit of the electrical generator 1 (10), part of which leaks and enters the magnetic circuit of the stepping motor 6 (or 61 and 62), so that an electromotive voltage is induced in the drive coils of the stepping motor 6 (or 61 and 62).
While this induction action is not to a degree that directly influences the rotational movement of the stepping motor 61 (or 61 and 62), if it occurs at a time with a bad timing when there is much induced electromotive voltage noise caused by the electrical generation when the drive judging means of the load compensation function is operating, because it is not possible to distinguish this with respect to induced electromotive voltage cause by free vibration of the rotor of the stepping motor 6 (or 61 and 62), it is not possible to avoid the danger that even if the rotor is not feed by 1 step, a judgment could be made that feed was done, so that the compensation drive pulse b which is actually required is not supplied.
According to experiments, over a practically usable eccentric weight rpm range (for example, 120 to 250 rpm), there is generation in the frequency range from 167 to 333 Hz, with a single-ended amplitude of 50 mV or greater, and when the weight free-falls, there is generation of induced voltage noise at 175 Hz at a level of 1 V or greater, this being a level that could not possibly be neglected.
There is also technology that appears to be applicable in solving this drawback. This will be described below as the third background art.
Specifically, the above-noted technology is disclosed in the publicly known Japanese Examined Patent Publication (KOKOKU) Nos. 61-28313 and 61-38423.
The underlying technology is a load compensation technology that is close to the technology of the first background art, this being a drive technology to which is added a function to provide a countermeasure with respect to an external alternating current magnetic field.
If a watch is placed within an external floating AC magnetic field that varies, because the magnetic flux thereof passes through the core of the coil with high density, an induced voltage develops in the coil, this causing misoperation of the drive judging means in the same manner as described with regard to the second background art, thereby hindering the achievement of complete load compensation.
In the third background art, the drive judging means is caused to operate also immediately before each normal drive (since the rotor is still stopped, this being only for the detection of external magnetic noise), and if an induced voltage is detected a normal drive pulse having a pulse widened to a priorly prepared value is supplied so that a feed error does not occur even in the presence of an external magnetic field, the operation of the drive judging means being omitted after drive.
In the case in which an external magnetic field is not detected, after a normal drive the drive judging means is caused to operate, and normal load compensation is performed.
While the above-noted cited references do not mention an application to an self-winding electrical generating watch, in the latter thereof it appears that there is sufficient possibility of such application, since the only difference is that the source of the noise magnetic field is within the watch.
However, a careful investigation reveals that, in a self-winding wristwatch, because of a sudden change in the electrical generation, there is a change in the noise generation condition even before and after the normal drive pulse, so that even if noise is not detected immediately therebefore, there is a frequent risk that noise generated during the immediately following drive judging period will cause misoperation.
Therefore, even the application of the third background art does not enable the achievement of a complete load compensation function.
An object of the present invention is to provide an improvement on the above-noted drawbacks in the background art, by providing a technology for use in an analog-type watch having a load compensation function means and which has an electrical generator capable of generating electricity intermittently, such as shown by examples cited with regard to self-winding electrical generation technology, this technology completing avoiding the influence of magnetic noise which accompanies the electrical generation action, thereby performing failure-free load compensation.